As a sensor for sensing an obstacle when a robot is autonomously moving or a sensor for sensing a person, there is, for example, a laser range finder (LRF).
Conventional laser range finders perform measurement of a time from when a laser light is output to when a reflected light, which is the laser light striking an object and being reflected, returns and calculates a distance to the object from a measurement result. The laser range finders, by changing a direction in which the laser light is output in a horizontal direction and a vertical direction, perform measurement of the distance to the object in an entirety of a range where measurement of the distance is performed (referred to hereinbelow as “scanning range”).
The conventional laser range finders comprise, for example, a laser diode (LD) that outputs the laser light, a mirror that adjusts an output direction of the laser light, a light-receiving element that receives the reflected light from the object, and a signal processing unit. As the minor that adjusts the output direction of the laser light, there is, for example, a mirror installed to a rotation mechanism, a polygon minor, a MEMS (Micro Electro Mechanical System) mirror, and the like. The signal processing unit outputs an output signal that causes the laser diode to output the laser light and accepts a light-receiving signal from the light-receiving element. The signal processing unit measures the distance to the object from a difference between a phase of the laser light output from the laser light and a phase of the reflected light received by the light-receiving element.
To precisely perform measurement of the distance by the conventional laser range finders, more accurately seeking an angle in the horizontal direction and an angle in the vertical direction of when the object is detected is desired.
As a method of seeking the angle in the vertical direction, there is disclosed, for example, a method that adds a light-receiving element to each end portion of a scanning range in a vertical direction and seeks a range of an amplitude from a timing at which the light-receiving elements detect a laser light (for example, see Patent Literature 1).